WASHINGTON (CNN) -- More than 170 people around the globe, including at least 61 in the United States, have been arrested in a major operation targeting international child pornographers, officials said Friday.

Attorney General Michael Mukasey and European Union representatives announced the sting's results Friday.

Operation Joint Hammer has rescued 11 girls in the United States, ages 3 to 13, who were sexually abused by child pornography producers, U.S. Attorney General Michael Mukasey and representatives of the European Union said at the Justice Department.

Dozens more were located in Europe, including several young female victims in Ukraine.

Authorities found connections between producers, distributors and customers in nearly 30 countries as a single investigation grew to a global inquiry into the dark corners of brutality and child abuse.

The investigation, code-named Operation Koala in Europe, was developed when investigators determined that a pornographic video found in Australia had been produced in Belgium.

"This joint EU-U.S. coordinated effort began with the discovery in Europe of a father who was sexually abusing his young daughters and producing images of that abuse," Mukasey said.

Further investigation showed a number of online child porn rings. Some included dangerous offenders who not only traded child pornography but also sexually abused children, the officials said.

Agents are still attempting to locate child victims whose images have appeared in photos and videos, and more arrests are expected as the FBI, Immigration and Customs Enforcement and the Postal Inspection Service continue the investigation.

A Postal Service official said ringleaders primarily targeted prepubescent female victims to satisfy their customers but noted that other groups produce photos and videos of boys and girls of all ages -- or even infants.